Oxidative dehydrogenation with manganese ferrite catalyst

ABSTRACT

1. IN A PROCESS FOR OXIDATIVE DEHYDROGENATION OF HYDROCARBONS HAVING 2 TO 12 CARBON ATOMS, AT LEAST ONE   &gt;CH-CH&lt;   GROUPING AND A BOILING PHASE COMPRISING CONTACTING A SAID HYDROCARBONS IN THE PRESENCE OF OXYGEN AT A TEMPERATURE OF GREATER THAN 250* C. WITH A CATALYST WHEREIN THE IMPROVEMENT COMPRISES EMPLOYING AS THE CATALYST A MANGANESE FERRITE CONTAINING 0.1 TO 20 WEIGHT PERCENT OF CARBON BLACK PREPARED BY INTIMATELY MIXING SAID CARBON BLACK WITH THE PRECURSORS OF THE MANGANESE FERRITE AND THEN REACTING THE PRECURSORS TO FORM THE MANGANESE FERRITE IN AN ATOMSPHERE CONTAINING LESS THAN 15 MOLE PERCENT OXYGEN.

United Statcs Patent 3,849,511 OXIDATIVE DEHYDROGENATION WITH MANGANESE FERRITE CATALYST Harold E. Manning, Houston, Tex., assignor to Petro-Tex Chemical Corporation, Houston, Tex.

No Drawing. Original application Oct. 7, 1970, Ser. No. 78,956, now Patent No. 3,751,385. Divided and this application July 30, 1973, Ser. No. 385,012

Int. Cl. C07c 5/18 US. Cl. 260-680 E 7 Claims ABSTRACT OF THE DISCLOSURE The presence of 1 to 20 weight percent carbon black in a manganese ferrite oxidative dehydrogenation catalyst improves the yields from oxidative dehydrogenation reactions employing such catalyst. The presence of about 5 Wt. percent carbon black in a manganese ferrite containing chromium as a promoter result in up to 7.3% absolute increase in yield in the oxidative dehydrogenation of isoamylene as compared to the catalyst prepared under the same conditions Without carbon black.

This is a division of application Ser. No. 78,956, filed Oct. 7, 1970, now U.S. Pat. No. 3,751,385.

This invention relates to oxidative dehydrogenation of organic compounds having at least one grouping. More particularly the invention relates to the use of manganese ferrite catalyst in such oxidative dehydrogenation. Specifically the invention relates to manganese ferrite catalysts prepared in a particular manner.

It is known to dehydrogenate organic compounds by contacting the compounds to be dehydrogenated at an elevated temperature preferably in the presence of catalysts. One method of dehydrogenation is known as oxidative dehydrogenation. According to this process, hydrogen released from the organic compounds reacts with oxygen to form water. One of the principal defects in oxidative dehydrogenation reactions is that quite often the reactions are unselective and oxygenated compounds are formed instead of the desired dehydrogenated compounds. These nonselective reactions are particularly evident when the compound to be dehydrogenated contains three or more carbon atoms. For example, when methyl butene is reacted with oxygen, a variety of products other than isoprene are possible as hydrocarbons and oxygenated hydrocarbons of various general mixtures may result. Also, combustion of the hydrocarbon may result in the formation of C0, C0 and water.

It is therefore one of the principal objectives of this invention to provide a process and catalyst wherein the organic compound is dehydrogenated preferably to a product having the same number of carbon atoms at a high level of conversion and selectivity. Another principal objective is to provide a process wherein the catalyst has long catalyst life. Other objectives of this invention are to provide a process wherein it is possible to have substantial quantities of steam present in the dehydrogenation zone, a high over-all throughput and a low contact time in the dehydrogenation zone and a process which has good control of reaction temperature. These and other objectives may be achieved by the process of this invention.

Briefly stated, one aspect of the present invention is an oxidative dehydrogenation catalyst comprising a manganese ferrite containing a minor amount of carbon black. Generally the manganese ferrite will contain from about .1 to 20 weight percent of carbon black based on the other catalyst components preferably about 1 to 15 weight percent and more preferably about 2 to 10 weight percent.

In addition to carbon black catalyst binding agents or fillers may be used, but the carbon black and said binders and fillers will not ordinarily exceed about 50 percent or 60 percent by weight of the catalysts and the described catalytic compositions will preferably constitute the main active constituent. These binding agents and fillers will preferably be essentially inert. Preferred catalysts are those that have at least 25 or preferably 50 weight percent of the defined catalyst actives. Also preferably iron will constitute at least 50 atomic weight percent of the cations in the catalyst. Unless stated otherwise, the compositions in this application are the main active constituents of the dehydrogenation process during dehydrogenation and any ratios and percentages refer to the surface of the catalyst in contact with the gaseous phase during dehydrogenation.

The catalysts of this invention comprise manganese ferrite produced in a particular manner. Manganese ferrite comprises a complex crystalline structure comprising manganese, iron and oxygen. According to this invention superior catalysts can be formed by producing the manganese ferrite by reacting the precursors of the manganese ferrites after the precursors have been intimately mixed with carbon black.

Manganese ferrite formation may be accomplished by reacting an active compound of iron with an active compound of manganese. By active compound is meant a compound which is reactive under the conditions to form the ferrite.

The starting materials may be such as oxides, hydroxides, or salts including oxalates, acetates, formates, sulfates, nitrates, halides, hydrates and so forth. Suitable manganese compounds are such as manganese oxalate, manganese hydroxide, manganese nitrate, manganese carbonate, manganese salts of aliphatic monocarboxylic acids of 1 to 5 carbon atoms, manganese sulfates, salts of aliphatic alcohols of 1 to 5 carbon atoms, hydrates thereof and mixtures thereof. The same classes of iron compounds may be employed such as iron nitrate, etc. The inorganic salts give excellent results.

The iron and manganese precursor components and carbon black can be combined in any conventional manner which will provide an intimate mixture, for example, manganese oxide, iron oxide and carbon black can be mixed in a slurry or dry mixed. One component can be deposited on another or the precursor components can be coprecipitated.

One procedure for forming the catalysts is to prepare an aqueous mixture of the precursor salts and thereafter this mixture can then be precipitated by mixing with a basic reactant to precipitate the precursor of the ferrite. Any suitable base may be employed but those containing unwanted cations will, of course, be less desirable. Volatile bases such as ammonium hydroxide or carbonate may be employed.

The temperature used for ferrite formation may be varied, depending somewhat upon the particular starting materials and upon the conditions present during ferrite formation. At any rate, superior catalysts are produced at temperatures of from high enough to form the ferrite to 800 C. with a preferred range being from between produced at temperatures of less than 700 C. Suitable temperatures of reaction are such as between about 400 to 800 C. with 10 a preferred range being from between about 500* to 700 C.

Another factor in producing superior catalysts is the rate of heating of the reactants to form the ferrite. Here again the rate of heating will be dependent upon the particular reactants and conditions employed, but better results are generally obtained when the reactants are heated at a rate of no greater than about 250 C. per minute and still better results are ordinarily obtained when the rate is no greater than about 100 C. per minute.

The ferrites are preferably prepared in an atmosphere containing little or no oxygen. Preferably the atmosphere will contain less oxygen than air, i.e., less than about mole percent oxygen. More preferably the calcining atmosphere will be substantially free of oxygen. Suitable atmospheres are gases such as nitrogen, helium, argon, neon, krypton, xenon and the like or mixtures thereof.

Improved manganese ferrite compositions may be obtained by utilizing halogen or halogen compounds during the formation of the ferrite. The use of halogen or halogen compounds in this manner is claimed in a copending Application by Philip M. Coiling and Johnny C. Dean, Ser. No. 671,236, now Pat. No. 3,567,793, issued Mar. 2, 1971, entitled Oxidative Dehydrogenation of Organic Compounds. An example of the use of a halogen would be the addition of manganese chloride to the reactants prior to the formation of the ferrite. Normally, chlorine is the preferred halogen so used.

The manganese ferrite compositions of this invention may also comprise additives. Phosphorus, silicon or mixtures thereof are examples of additives. For instance, phosphorus and/or silicon may suitably be present in an amount of from about 0.2 to weight percent based on the total weight of the atoms of iron and manganese. These ingredients may contribute e.g. to the stability of the compositions. The silicon, phosphorus or other additives may be added at various stages of the preparation of the composition, or may be added to the already formed manganese ferrite. Any suitable compounds may be employed such as phosphoric acid, phosphorus pentoxide, ethyl phosphate, ammonium phosphate, silicon halides, etc.

It has been found that a particularly useful manganese ferrite is one that contains a small amount of chromium in the crystalline lattice. Up to about 0.4 atom of chromium per atom of manganese may be used, preferably about 0.05 to 0.2 atoms. It has been observed that the presence of chromium in the lattice increases the lattice constant. One proposed mechanism for the oxidative dehydrogenations described hereinafter supposes that the iron in the lattice is the active site for the catalytic effect. By adjusting the lattice distance between the iron sites in the catalyst within the distance between carbon atoms in the molecule of the reacting organic compound a more efficient reaction occurs. It is believed that the presence of the specified amounts of chromium in the crystalline lattice more nearly obtains the proper distance. Of course the proposed mechanism is no part of the present invention nor of any invention in regard to chromium containing manganese ferrites and no reliance is placed thereon in regard to patentability. The chromium is incorporated into ferrite preferably by combining a reactive chromium compound with the reactive iron and manganese compounds and carbon black prior to reacting to form the ferrite. Suitable reactive materials are chromium oxide, chromium oxalate, chromium acetate, chromium sulfate and the like, as previously described for the iron and manganese starting material.

These manganese ferrite compositions may be reduced with a reducing gas prior to use in the process of dehydrogenation. Examples of reducing gases are hydrogen or hydrocarbons. For example, the manganese ferrite compositions may be reduced with e.g. hydrogen at a temperature of at least 250C. with the temperature of reduction generally being no greater than 850 C. By reducing gas is meant a gas that will react with oxygen under the conditions of reduction. However, it is one of the advantages of this invention that the manganese ferrites prepared according to this invention may not require reduction prior to use in the dehydrogenation reaction.

According to this invention it has been found that the preferred manganese ferrite compositions exhibit a certain type of X-ray diffraction pattern. The preferred compositions do not have as sharp X-ray diffraction reflection peaks as would be found, e.g., in a high crystalline material having the same chemical composition. Instead, the preferred catalyst of this invention exhibit reflection peaks which are relatively broad. The degree of sharpness of the reflection peak may be measured by the reflection peak band width at half height (W h/2). In other words, the width of the reflection peak as measured at one-half of the distance to the top of the peak is the band width at half height. The band width at half height is measured in units of 2 theta. Techniques for measuring the band widths are discussed, e.g., in Chapter 9 of Klug and Alexander, X-ray Diffraction Procedures, John Wiley and Son, N.Y., 1954.

According to one theory of manganese ferrite preparation it is considered that maintenance of the manganese precursor in the +2 valance stage during the formation stage of the ferrite contributes to superior catalytic properties. Under this assumption it can be further theorized that carbon black acts as an oxygen scavenger to help maintain the +2 of the manganese. As stated before the mechanism is merely suppositive and although it may be of aid to those skilled in this art in understanding the invention, no reliance is placed thereon for patentability, nor is it intended that the instant invention or any derived herefrom be in any way limited or restricted because of such theoretical mechanisms.

The process of this invention may be applied to the dehydrogenation of a great variety of organic compounds to obtain the corresponding unsaturated derivative thereof. Such compounds normally will contain from 2 to 20 carbon atoms, at least one grouping, a boiling point below about 350 C., and such compounds may contain other elements, in addition to carbon and hydrogen such as oxygen, halogens, nitrogen and sulphur. Preferred are compounds having from 2 to 12 carbon atoms, and especially preferred are compounds of 2 to 6 or 8 carbon atoms.

Among the types of organic compounds which may be successfully dehydrogenated to the corresponding unsaturated derivative by means of the novel process of this invention are nitriles, amines, alkyl halides, ethers, esters, aldehydes, ketones, alcohols, acids, alkyl aromatic compounds, alkyl heterocyclic compounds, cycloalkanes, alkanes, alkenes, and the like. Illustration of dehydrogenations include propionitrile to acrylonitrile, propionaldehyde to acrolein, ethyl chloride to vinyl chloride, methyl isobutyrate to methyl methacrylate, 2 or 3-chlorobutene-1 or 2,3-dichlorobutane to chloroprene, ethyl pyridine to vinyl pyridine, ethylbenzene to styrene, isopropylbenzene to a-methyl styrene, ethylcyclohexane to styrene, cyclohexane to benzene, ethane to ethylene, propane to propylene, isobutane to isobutylene, n-butane to butene and butadiene-l,3, butene to butadiene-1,3 and vinyl acetylene, methyl butene to isoprene, cyclopentane to cyclopentene and cyclopentadiene-1,3, n-octane to ethyl benzene and ortho-xylene, monomethylheptanes to xylenes, propane to propylene to benzene, ethyl acetate to vinyl acetate, 2,4,4-trimethylpentane to Xylenes, and the like. This invention may be useful for the formation of new carbon to carbon bonds by the removal of hydrogen atoms such as the formation of a carbocyclic compound from two aliphatic hydrocarbon compounds or the formation of a dicyclic compound from a monocyclic compound having an acyclic group. Examples of conversions are the conversion of n-heptane to toluene and propene to diallyl.

Representative materials which are dehydrogenated by the novel process of this invention include ethyl toluene, alkyl chlorobenzenes, ethyl naphthalene, isobutyronitrile, propyl chloride, isobutyl chloride, ethyl fluoride, ethyl bromide, n-pentyl iodide, ethyl dichloride, 2,3-dichlorobutane, 1,3-dichlorobutane, 1,4-dichlorobutane, the chloroiiuoroethanes, methyl pentane, methylethyl ketone, diethyl ketone, n-butyl alcohol, methyl propionate, and the like. This invention is particularly adapted to the preparation of vinylidene compounds containing at least one group, that is, a group containing a terminal methylene group attached by a double bond to a carbon atom, and having 2 to 12 carbon atoms by the dehydrogenation of compounds of the formula CH CH R wherein R is an organic radical of from 0 to carbon atoms, preferably a hydrocarbon. Similarly, acetylenic compounds of the formula CHEC- may be produced from the same starting materials.

Preferably oxygen is employed, suitably in an amount within the range of 0.2 to about 5.0 moles of oxygen per mole of organic compound to be dehydrogenated, preferably from 0.2 to 2.5 moles per mole. Generally, better results may be obtained if the oxygen concentration is maintained between about 0.25 and about 1.6 moles of oxygen per mole of organic com-pound to be dehydrogenated, such as between 0.35 and 1.2 moles of oxygen. The oxygen may be fed to the reactor as pure oxygen, as air, as oxygen-enriched air, oxygen mixed with diluents, and so forth. 'Based on the total gaseous mixture entering the reactor, good results are obtained with oxygen present in an amount from about 0.5 to 25 volume percent of the total gaseous mixture, such as in an amount from about 1 to volume percent of the total. The total amount of oxygen utilized may be introduced into the gaseous mixture entering the catalytic zone or sometimes it has been found desirable to add the oxygen in increments, such as to different sections of the reactor. The above described proportions of oxygen employed are based on the total amount of oxygen used. The oxygen may be added directly to the reactor or it may be premixed, for example, with a diluent or steam. It is also Within the scope of this invention to employ the described manganese compositions as the partial or sole source of oxygen used for oxidative dehydrogenation. For example, the manganese composition-s may reelase oxygen to react with the organic compound during a dehydrogenation step and thereafter the manganese composition is regenerated by oxidation prior to another step where oxygen is released. Preferably such a process will have the manganese composition present as a moving bed.

It is one of the advantages of this invention that halogen may also be added to the reaction gases to give excellent results. The addition of halogen to the feed is particularly effective when the hydrocarbon to be dehydrogenated is saturated. The halogen present in the dehydro genation zone may be either elemental halogen or any compound of halogen which would liberate halogen under the conditions of reaction. Suitable sources of halogen are such as hydrogen iodide, hydrogen bromide andhydrogen chloride; aliphatic halides, such as ethyl iodide, methyl bromide, 1,2-dibromo ethane, ethyl bromide, amyl bromide, and allyl bromide; cycloaliphatic halides, such as cyclohexylbromide; aromatic halides, such as benzyl bromide; halohydrins, such as ethylene bromohydrin; halogen substituted alphatic acids, such as bromoacetic acid; ammonium iodide; ammonium bromide; ammonium chloride; organic amine halide salts, such as methyl amine hydrobromide; metal halides including molten halides; and the like. Mixtures of various sources of halogen may be used. The preferred sources of halogen are iodine, bromine, and chlorine, and compounds thereof, such as hydrogen bromide, hydrogen iodide, hydrogen chloride, ammonium bromide, ammonium iodide, ammonium chloride, alkyl halides of one to six carbon atoms and mixtures thereof, with the iodine and bromine compounds, especially the ammonium compounds, being particularly preferred. When terms such as halogen liberating materials or halogen materials are used in the specification and claims, this includes any source of halogen such as elemental halogens, hydrogen halides, or ammonium halides. The amount of halogen, calculated as elemental halogen, may be as little as about 0.0001 or less mole of halogen per mole of the organic compound to be dehydrogenated to as high as 0.2 or 0.5. The preferred range is from about 0.001 to 0.09 mole of halogen per mole of the organic compound to be dehydrogenated.

The temperature for the dehydrogenation reaction generally will be at least about 250 C., such as greater than about 300 C. or 375 C., and the maximum temperature in the reactor may be about 650 C. or 750 C. or perhaps higher such as 900 C. under certain circumstances. However, excellent results are obtained within the range of or about 300 C. to 575 C., such as from or about 325 C. to or about 525 C. The temperatures are measured at the maximum temperature in the dehydrogenation zone. An advantage of this invention is that lower temperatures of dehydrogenation may be utilized than are possible in conventional dehydrogenation processes. Another advantage is that large quanti-ties of heat do not have to be added to the reaction.

The dehydrogenation reaction may be carried out at atmospheric pressure, superatmospheric pressure or at sub-atmospheric pressure. The total pressure of the sys term will normally be about or in excess of atmospheric pressure, although sub-atmospheric pressure may also desirably be used. Generally, the total pressure will be between about 4 p.-s. i.a. and about or p.s.i.a. preferably, the total pressure will be less than about 75 p.s.i.a. and excellent results are obtained at about atmospheric pressure.

The initial partial pressure of the organic compound to be de'hydrogenated will preferably be equivalent to, equal to, or less than one-half atmosphere at a total pres-sure of one atmosphere. Generally, the combined partial pres sure of the organic compound to be dehydrogenated, together wit-h the oxygen in gaseous phase will also be equivalent to less than one-half atmosphere at a total pressure of one atmosphere. Preferably, the initial partial pressure of the organic compound to be dehydrogenated will be equivalent to no greater than one-third atmosphere or no greater than one-fifth atmosphere at a total pressure of one atmosphere. Reference to the initial parti-al pressure of the organic compound to be dehydrogenated means the partial pressure of the organic compound as it first contacts the catalytic particles. An equivalent partial pressure at a total pressure of one atmosphere means that one atmosphere total pressure is a reference point and does not imply that the total pressure of the reaction must be operated at atmospheric pressure. For example, in-a mixture of one mole of ethyl chloride, three moles of steam, and one mole of oxygen under a total pressure of one atmosphere, the ethyl chloride would have an absolute pressure of one-fifth of the total pressure, or roughly six inches of mercury absolute pressure. Equivalent to this six inches of mercury absolute pressure at atmospheric pressure would be ethyl chloride mixed with oxygen under a vacuum such that the partial pressure of the ethyl chloride is 6 inches of mercury absolute. The combination of a diluent such as nitrogen, together with the use of a vacuum, may be utilized to achieve the desired partial pressure of the organic compound. For the purpose of this invention, also equivalent to the six inches of mercury ethyl chloride absolute pressure would be the same mixture of one mole of ethyl chloride, three moles of steam, and one mole of oxygen under a total pressure greater than atmospheric, for example, a total pressure of 20 -p.s.i.a. Thus, when the total pressure in the reaction zone is greater than one atmosphere, the absolute values for the pressure of the organic compound to be dehydrogenated will be increased in direct proportion to the increase in total pressure above one atmosphere.

Prefer-ably, the reaction mixture contains a quantity of steam, with the range generally being between about 2 and 40 moles of steam per mole of organic compound to be dehydrogenated. Preferably, steam will be present in an amount from about 3 to 35 moles per mole of organic compound to be dehydrogenated and excellent results have been obtained within the range of about 5 to about 30 moles of steam per mole of organic compound to be dehydrogenated. The functions of the steam are several-fold, and the steam may not merely act as a diluent. Diluents generally may be used in the same quantities as specified for the steam.

The gaseous reactants may be conducted through the reaction chamber at a fairly wide range of flow rates. The optimum flow rate Will be dependent upon such variables as the temperature of reaction, pressure, particle size, and whether a fluid bed or fixed bed reactor is utilized. Desirable flow rates may be established by one skilled in the art. Generally, the flow rates will be within the range of about 0.10 to 25 liquid volumes of the organic compound to be dehydrogenated per volume of dehydrogenation zone containing catalyst per hour (referred to as LHSV), wherein the volumes of organic compound are calculated at standard conditions of C. and 760 mm. of mercury. Usually, the LHSV will be between 0.15 and about or 10. For calculation, the volume of reactor containing catalyst is that volume of reactor space including the volume displaced by the catalyst. For example, if a reactor has a particular volume of cubic feed of void space, when that void space is filled with catalyst particles, the original void space is the volume of reactor containing catalyst for the purpose of calculating the flow rate. The gaseous hourly space velocity (GHSV) is the volume of the organic compound to be dehydrogenated in the form of vapor calculated under standard conditions of 0 C. and 760 mm. of mercury per volume of reactor space containing catalyst per hour. Generally, the GHSV will be between about 25 and 6400, and excellent results have been obtained between about 38 and 3800. Suitable contact times are, for example, from about 0.001 or higher to about 4 or or 25 seconds, with particularly good results being obtained between 0.01 and 5 seconds. The contact time is the calculated dwell time of the reaction mixture in the reaction zone, assuming the moles of product mixture are equivalent to the moles of feed mixture. For the purpose of calculation of contact times, the reaction zone is the portion of the reactor containing catalyst which is at a temperature of at least 250 C.

The dehydrogenation reactor may be of the fixed bed or fluid bed type. Conventional reactors for the production of unsaturated organic compounds by dehydrogenation are satisfactory. Excellent results have been obtained by packing the reactor with catalyst particles as the method of introducing the catalytic surface. The catalytic surface may be introduced as such or it may be deposited on a carrier by methods known in the art such as by preparing an aqueous solution or dispersion of a catalytic material and mixing the carrier with the solution or dispersion until the active ingredients are coated on the carrier. If a carrier is utilized, very useful carriers are silicon carbide, aluminum oxide, pumice, and the like. Other known catalyst carriers may be employed. When carriers are used, the amount of catalyst on the carrier will suitably be between about 5 to 75 weight percent of the total weight of the active catalytic material plus carrier, Another method for introducing the required surface is to utilize as a reactor a small diameter tube wherein the tube wall is catalytic or is coated with catalytic material. Other methods may be utilized to introduce the catalytic surface such as by the use of rods, wires, mesh, or shreds, and the like, of catalytic material.

In the following examples the conversions, selectivities and yields are reported in mole percent. Otherwise, all percentages are weight percent unless expressed to the contrary. The apparatus used in the oxidative dehydrogenations consisted of a vertical fixed bed reactor containing thermocouples at spaced intervals throughout the bed. The temperature reported for each dehydrogenation is the maximum temperature in the bed. The efiluent from the reactor was condensed and analyzed immediately by vapor phase chromatography.

EXAMPLE 1 Catalyst Preparation TABLE I Grams Catalyst Catalyst Materials A B Manganous carbonate b (assay 43.6% Mn) Mangaynfus chloride b (MuClz-4H1O; assay 99.3 0 Chromium oxide 22. 8 Distilled water 1300 Carbon black 0 50. 0

8 Williams yellow hydrated a-FezOa, YLO.1788. 11 Baker analyzed reagent grade. 0 Baker (C.P.). d Cabot, Black Pearls-74.

Portions of catalyst A and B were each calcined at 600 C. and 700 C. as indicated above. Portions of each of these calcined products were prepared for use by depositing 76 grams of the calcined product and 2.3 grams of 86% H PO onto grams of HCl leached 6-9 mesh AMC alumina. X-ray scan indicated that a manganese ferrite was the predominate material in each calcined product. The catalysts are designated by letter and calcination temperature, viz,

A600 A700 B600 B700 The same amount of each catalyst was employed for the runs in Example 2 in the reactor as described.

EXAMPLE 2 Oxidative Dehydrogenation A feed of isoamylenes (85.4% Z-methyl butane-1 0.7%-pentane, 2.9% isopentane, 2.8% other C and 0.1 heavy ends) was fed at 1.5 LHSV, mole ratio of steam/ 0 /hydrocarbon of 30/.9/1. In Table II the catalysts, hours, maximum temperatures and results are reported.

TABLE II Isoprene mole, percent Hours on Temp, Conver- Selectiv- Run Catalyst stream F., max. sion ity Yield 1 The catalyst loaded in the reactor and reduced for two hours at 840 F. with 100 vols.

of Hz/VOl. of catalyst/hr.

2 After 97 hours on stream the hydrocarbon was discontinued and the catalyst reduced at 840 F. for 2 hours with 100 vols. of Hzlvol. of catalyst/hr.

I l grouping and a boiling point below about 350 C. in vapor phase comprising contacting said hydrocarbons in the presence of oxygen at a temperature of greater than 250 C. with a catalyst wherein the improvement comprises employing as the catalyst a manganese ferrite containing 0.1 to 20 weight percent of carbon black prepared by intimately mixing said carbon black with the precursors of the manganese ferrite and then reacting the precursors to form the manganese ferrite in an atmosphere containing less than 15 mole percent oxygen.

2. The process according to claim 1 wherein the mangalinese ferrite contains 1 to 15 weight percent carbon b ack.

3. The process according to claim 2 wherein the manganese ferrite contains 2 to 10 weight percent carbon black.

4. The process according to claim 3 wherein the manganese ferrite contains up to 0.4 atom of chromium per atom of manganese in the crystalline lattice of the ferrite.

5. The process according to claim 4 wherein the atom ratio of chromium to manganese in the ferrite is in the range of 0.05:1 to 0.2: 1.

6. The process according to claim 5 Where the hydrocarbon comprises isoamylene.

7. The process according to claim 1 wherein the manganese ferrite is prepared in an atmosphere substantially free of oxygen.

References Cited UNITED STATES PATENTS PAUL M. COUGHLAN, JR., Primary Examiner US. Cl. X.R. 260-680 D, 683.3

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 511 Dated November 19, 1974 Inventor(s) Harold E. Manning It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 2, line 60, paragraph beginning at line 60 should read The temperature used for ferrite formation may be varied, depending somewhat upon the particular starting materials and upon the conditions present during ferrite formation. At any rate, superior catalysts are produced at temperatures of from high enough to form the ferrite to 800 C. or less. Still -better catalysts are ordinarily produced at temperatures of less than 700 C. Suitable temperatures of reaction are such as between about 400 to 800 C. with a preferred range being from between about 500 to 700 C.

Col. 3, line 48 reads "within" but should read with Col. 6, line 75 reads "pressure would be" but should read pressure at atmospheric pressure would be 3 Col. 8, line 38 (Table I, l tem lunder Materials) reads "Fe O b t should read Fe O Col. 8, line 39 (Under Catalyst A) reads "533. 5" but should read Signed and sealed this 3rd day of June 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C n l-iASON Commissioner of Patents Attesting Officer and Trademarks 

1. IN A PROCESS FOR OXIDATIVE DEHYDROGENATION OF HYDROCARBONS HAVING 2 TO 12 CARBON ATOMS, AT LEAST ONE 